Hello,


I have four doubts:

1)
why gzAzymuth is giving me Northern direction in this case, for example?

require(sp); require(rgdal)

kk=data.frame(x=c(575552.8,576295.9), y=c(4103900,4103611))
coordinates(kk)=~x+y
plot(kk, typ="o", col=4)
gzAzimuth(coordinates(kk)[1,], coordinates(kk)[2,])

2) how to cut a polygon (for example a border file) into chuncks? (i.e. 
separate areas, according to a line)

3) how to create multiple polygons, from a grid file, according to a 
criteria. For example, :

require(gstat)
data(meuse)
coordinates(meuse) = ~x+y
data(meuse.grid)
gridded(meuse.grid) = ~x+y
m <- vgm(.59, "Sph", 874, .04) # ordinary kriging:
x <- krige(log(zinc)~1, meuse, meuse.grid, model = m)
spplot(x["var1.pred"], main = "ordinary kriging predictions")
# how to create a polygon with the areas greater than 5...


4) Is it defined in proj4, the datum lisboa, Sistema of Hayford- Gauss 
Militar? and UTM, using zone 29N (29 is down here, for example...)?
CRS("+proj=utm +zone=29 +datum=WGS84")

How do we specify it?


Thank you very much in advance,... any help will be much appreciated...
Best regards,
Marta

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